diff --git a/src/sensor_state_data/__init__.py b/src/sensor_state_data/__init__.py
index e1ff494..f83afdd 100644
--- a/src/sensor_state_data/__init__.py
+++ b/src/sensor_state_data/__init__.py
@@ -3,7 +3,13 @@
 from .base import BaseDeviceClass
 from .binary_sensor.device_class import BinarySensorDeviceClass
 from .data import SensorData, SensorDeviceInfo, SensorUpdate
-from .description import BinarySensorDescription, SensorDescription
+from .description import (
+    BaseBinarySensorDescription,
+    BaseDescription,
+    BaseSensorDescription,
+    BinarySensorDescription,
+    SensorDescription,
+)
 from .device import DeviceKey
 from .device_class import DeviceClass
 from .library import SensorLibrary
@@ -12,7 +18,10 @@
 from .value import BaseValue, BinarySensorValue, Event, SensorValue
 
 __all__ = [
+    "BaseBinarySensorDescription",
+    "BaseDescription",
     "BaseDeviceClass",
+    "BaseSensorDescription",
     "BaseValue",
     "BinarySensorValue",
     "BinarySensorDescription",
diff --git a/tests/test_public_api.py b/tests/test_public_api.py
new file mode 100644
index 0000000..338cbb8
--- /dev/null
+++ b/tests/test_public_api.py
@@ -0,0 +1,28 @@
+"""Public API surface contract."""
+
+import sensor_state_data
+from sensor_state_data import (
+    BaseBinarySensorDescription,
+    BaseDescription,
+    BaseSensorDescription,
+    SensorLibrary,
+)
+
+
+def test_base_description_classes_importable_from_root():
+    """Base description classes are part of the public API."""
+    assert issubclass(BaseSensorDescription, BaseDescription)
+    assert issubclass(BaseBinarySensorDescription, BaseDescription)
+
+
+def test_sensor_library_entries_are_base_sensor_descriptions():
+    """SensorLibrary exposes BaseSensorDescription instances, so the class
+    must be importable from the package root to annotate/check them."""
+    entry = SensorLibrary.BATTERY__PERCENTAGE
+    assert isinstance(entry, BaseSensorDescription)
+
+
+def test_all_names_are_importable():
+    """Every name in __all__ resolves to a real attribute."""
+    for name in sensor_state_data.__all__:
+        assert hasattr(sensor_state_data, name), name